Just adding a data point here: I flew CX100 on the weekend and checkin opened close to three hours before the flight (a smidge early, actually, maybe 3h10m) - by which time there was already a massive line, and an ill-formed one because the bollards for business class, premium economy, luggage drop erc had not been put in place - resulting in some angry passengers and rather a bit of argy-bargy when some were seen to skip the queue and walk straight to the appropriate counter.

So, as you have bags to check, I would consider getting there rather early if you want to maximize lounge time for example.